The present invention refers to a device for connecting the bits with the cutting head of a drift advancing machine or the like.
For connecting the bits with a cutting head such that worn bits can easily be interchanged with new bits, and bits are supported within sleeve-shaped bit holders fixed to the cutting head. In known embodiments the bits are secured against falling out of the bit holders by threaded bolts or the like laterally threaded into the sleeve-shaped bit holders such that the bits are pressed against the inner wall of the bit holders and, respectively, by maintaining the bits in their position by spring elements. Such known arrangements suffer from the drawback that during operation of the drift advancing machine or the like, smaller particles of the exploited material and dust enter the bit holder and cause the bit as well as the threaded bolt and, respectively, the spring elements to become clamped within the bit holder so that, as a rule, a worn bit can only be removed with great difficulties.
The invention particularly refers to a device for connecting the bits with the cutting head of a drift advancing machine or the like, comprising sleeve-shaped bit holders fixed to the cutting head and accommodating the bits and aims at avoiding the drawbacks of known devices of the kind described. The invention essentially consists in that within a mounting obliquely arranged to the axis of the sleeve-shaped bit holder a locking bolt is pivotally supported and has a recess on one side of its front end protruding into the cavity of the bit holder, said front end extending in the locking pivotal position of the locking bolt into a recess of the bit, whereas in releasing pivotal position of the locking bolt the recess of the locking bolt is releasing the bit.
In a device according to the invention, the bit can be released by simply rotating the locking bolt for approximately one half revolution, noting that then the recess of the locking bolt does release the bit and the bit can be pulled out of the bit holder. Thus, for releasing the bit, it is only necessary to turn the locking bolt, which has no thread whatsoever, so that manipulation can be effected in a much more simple manner. The invention provides a device in which the bits can be interchanged without any effort and without the aid of special tools.
According to a further feature of th invention, the fron end of the locking bolt is extending with play into the recess of the bit, so that on operation the bit is not locked in place within the bit holder but is guided within the bit holder with some play and only secured by the locking bolt against falling out of the bit holder. In this manner, on operation some relative movement is allowed between the bit and the corresponding bit holder, and this relative movement has a result that any particles entering the bit holder are again forced out of the bit holder and cannot adhere to the inner wall of the bit holder and thus cause jamming of the bit.
According to the invention, the bit may have a flattening extending up to the end, accommodated within the bit holder, of the bit, the recess of the bit being worked into said flattening. With cylindrical bit shafts, this flattening is on introducing the bit into the bit holder cooperating with the locking bolt assuming releasing position, so that, when introducing the bit into the bit holder, a guide means is provided which ensures the correct position of the bit relative to the pivotable locking bolt even in releasing position of the locking bolt, so that the locking bolt can then without any difficulties be rotated into its locking position. According to the invention, the bit can alternatively be cylindrical in shape and have its recess formed of an annular groove, noting that conventiently that portion of the bit which is located between the annular groove and the end, accommodated within the bit holder, of the bit, is stepped to a reduced diameter. With such an embodiment, the bit is additionally allowed to rotate within the bit holder on operation, what contributes to preventing the bit to become jammed within the bit holder, which jamming would make the bit difficult to interchange.
Conveniently, the recess of the locking bolt is defined by an inclined plane extending from the front surface of the locking bolt, said inclined plane including with the locking bolt axis an angle .alpha. being at least of the same magnitude as that angle .beta. under which the locking bolt is inclined relative to the bit axis. In this case the inclined plane is, in releasing position of the locking bolt, parallel relative to the bit axis or including with this axis such an angle that removal of the bit from the bit holder is not obstructed by protruding parts in releasing position of the locking bolt and is acting as guiding surface for the bit to be removed.
According to a preferred embodiment, the locking bolt is obliquely arranged in direction to the bit and accommodated within the bit holder, so that the bit is more reliably anchored within the bit holder when exerting traction forces to the bit in a direction as to remove the bit from the bit holder.
Conveniently, the locking bolt is provided at its free end with an attachment for an engaging tool, said attachment being, for example, formed of a pin or a sleeve extending through the locking bolt, so that the locking bolt can be rotated in a simple manner.
According to the invention, the arrangement is conveniently such that the locking bolt is guided within a bushing threadedly introduced into the holder and is guided therein with interposition of an intermediate layer of high friction coefficient, and in that the front end of the locking bolt is formed as an enlarged head being supported against that bushing. In such an arrangement the locking bolt is exactly guided and reliably secured in position and, in addition, the locking bolt is on account of the intermediate layer prevented from unintentional rotation during operation and thus from becoming released. This arrangement additionally provides the possibility to easily interchange the entity consisting of locking bolt and bushing in case the locking bolt has become damaged.